Responding to concerns by DairyNZ that the endophyte AR37 ryegrass leads to lower summer and autumn milk production, the two organisations have jointly issued a statement qualifying concerns, but admitting AR37 produced less milksolids from the same pasture yield compared
with the older endophyte ryegrass, AR1.
DairyNZ's earlier press release warned its trials showed there could be a loss of 30kg of milksolids a cow over the season compared with cows grazing AR1 pasture.
The new, joint statement removes any reference to quantifying a production loss.
That statement said AR37 was more persistent than AR1 and would yield more dry matter over the medium term.
The two organisations also said that in a Waikato trial lasting one season, DairyNZ found no significant difference in annual milk solid production on a per cow basis between AR37 pasture and AR1 pasture.
"However, in three grazing trials and two indoor feeding trials there are seasonal differences, with the summer-autumn results showing statistically significantly more milk solids for AR1 over AR37 pastures.''
In early March, the statement said, AR37 pastures had double the tiller density of other treatments despite the continuing drought.
The AR37 pastures also persisted longer than AR1, produced more dry matter and no cows in the trials showed signs of ryegrass staggers from either AR1 or AR37 pasture.
Farmers are advised that while AR37 produced less milksolids from the same pasture yield, compared with AR1, there was evidence the new ryegrass was persistent and yielded more dry matter than AR1 over the medium term.
They recommend AR37 be used where AR1 did not persist but if the older endophyte ryegrass did persist, then farmers should stick with AR1.
Respected Dunedin scientist Jock Allison said 40% of a cow's lactation occurred during summer and autumn, the period when AR37 pastures produced fewer milksolids.
He said the loss of 30kg of milk solids over the summer-autumn period equated to a 23.1% loss in production for that period, based on average North Island cow production of 325kg of milksolids.
"Highly statistically significant over that period,'' he said.
Dr Allison reiterated earlier claims that AR37 had been over promoted and its performance did not match that promotion.